Conventional bicycles include a normally tubular frame with a front wheel capable of being steered by a handlebar, as well as a rear wheel equipped with a ratchet mechanism mounted on the rear wheel's hub. The ratchet mechanism is driven by a chain that extends around a sprocket driven by pedals mounted on cranks. This type of bicycle, according to the most varied types of configurations, has a seat on which a cyclist can sit. Nonetheless, the movement carried out by the user of this bicycle is a cyclical motion and therefore not natural, like walking.
Attempts have been made to introduce a type of drive for bicycles whereby a cyclist can ride a vehicle of this kind while in an erect position, as in U.S. Pat. No. 8,162,338, issued Apr. 24, 2012, where the rear portion of the proposed bicycle has a structure where the sprocket is mounted and connected to the ratchet mechanism via a chain. With this type of bicycle, the sprocket is driven by cranks that, instead of being equipped with conventional pedals, are linked to long rods whose ends include platforms for the cyclist's feet. One platform is provided for the right foot and another platform is provided for the left foot. Each platform has its own rod for connection to the crank.
In this type of bicycle, the front end of each platform for a cyclist's feet contains a pulley that moves on a tubular track positioned in a slightly tilted manner, so that the cyclist travels forward in an alternating manner on the platforms via elliptical movements that are similar to normal human striding. These movements are translated into an angular oscillating motion of the rods and are subsequently converted into the rotary motion of the sprocket to produce the corresponding movement of rotary motion of the ratchet mechanism connected to the hub of the rear wheel.
This type of bicycle has a series of disadvantages that, for example, include the fact that substantial alteration of a bicycle's structure is necessary in order to accommodate the sprocket/ratchet assembly located above the rear wheel in the rear portion, thus creating an unusually and excessively complex design structure with costs exceeding the normal costs associated with ordinary bicycles.
Another conventional design includes the design for a vehicle described by U.S. Pat. No. 7,803,090, issued Sep. 28, 2010. This vehicle is not actually a bicycle because it has three wheels, with two front wheels and one rear wheel.
The vehicle described in U.S. Pat. No. 7,803,090 is a hybrid tricycle with a drive system generically analogous to the one described in document U.S. Pat. No. 8,162,338, since it uses rods connected to mountings for the feet in order to directly move the rear wheel. This constitutes the drive unit for the vehicle.
The aforementioned tricycle consists of an elliptical machine that imitates normal human striding, and its steering is even more complex and is based on a design where simplicity is not a priority. It is also a relatively long, wide, and heavy machine, and therefore constitutes a limited means of transportation.
Additionally, in relation to these types of vehicles belonging to the state of the art and more specifically in terms of this last example of a three-wheeled vehicle, also known as “Street Strider,” a shared feature can be observed whereby both of them produce a form of movement of the cyclist's feet that can be regarded or defined as being essentially elliptical.
In general terms, the type of elliptical motion identified in the above two vehicles, and that can be defined as elliptical, has been found to be more efficient than the turning motion produced by more conventional bicycles, insofar as an elliptical trajectory more closely approximates the natural motion that characterizes human striding.